Should You Test a Patient for Clostridium difficile if They've Received a Laxative?

Automatic alerts can reduce unnecessary testing, which might produce false-positives.

Michael Nailor, PharmD

Testing for Clostridium difficile (C. difficile) infection is common among hospital patients who receive laxatives, though it may suggest a high rate of false-positives, according to recent findings.

The hospital system at Hartford Healthcare in Connecticut developed a smart alert system for prescribers that alerted them when a C. difficile test was ordered and the patient received a laxative within the prior 24 hours. This was based on the belief that patient-reported diarrhea was most likely as a result of the laxative and not the result of any C. difficile presence. Once notified, providers could decide to continue the testing or cancel. The study, based on 4 hospitals, examined how often the test was canceled or continued, and the outcomes of the tests.

Out of 366 patients, doctors received 483 alerts, the researchers learned. However, doctors overrode 75% of those alerts.

“The high rate of overrides by the providers, likely is a reflection of ‘alert fatigue’ or unaware of the possibility of false-positive results,” study author Michael Nailor, PharmD explained to MD Magazine. “Alert fatigue: providers receive lots of alerts from the electronic medical record when they order drugs, many of which are unnecessary, it creates a culture of overriding them without reading and evaluating each 1 fully in order to complete all of their other tasks.”

About a third of the tests that were ordered were never processed, because the patient no longer had diarrhea to test, according to the researchers. Among the remaining tests, about 80% were negative. The tests that went ahead anyway and came back positive looked clinically similar to patients who tested negative, particularly in terms of C. difficile symptom manifestation, which suggested they did not have the infection.

Overall, the alert avoided 74 tests over the 4 month period. There is an approximate cost of about $40 per test, which the investigators estimate represent a savings of about $3,000. They also predict an unknown saving in terms of labor cost, antimicrobial therapy costs, and cost of hospitalization in isolation for the patient.

When patients test positive for C. difficile infection, a series of events is triggered, such as isolation for the patient, the start of antibiotic therapy, and the government tracking rates of hospital-acquired C. difficile infection can reduce Medicare payments to the hospital if the numbers are higher than standard ranges.

“Hospitalists need more education regarding false positive C. difficile infection tests and to have a greater understanding that almost all patients who recently received a laxative don’t have C. difficile disease and shouldn’t be tested," Nailor added. “Automatic alerts informing providers of recent laxative use can be effective, but additional educational efforts are likely needed to further reduce unnecessary testing and the bad implications listed above.”

In an unrelated 2017 study, which surveyed clinicians who tested children for C. difficile infection despite awareness of laxatives or stool softeners administered the day before testing, some of the reasons for continuing the test included: changes in bowel movements since baseline, new onset abdominal pain, prior C. difficile history, recent antibiotic use, and high-risk clinical status.

The paper, titled “Evaluation of a best practice alert to reduce unnecessary Clostridium difficile testing following receipt of a laxative,” was published in the journal Diagnostic Microbiology & Infectious Disease.